The (Essential) Commercial Flat Roof Ventilation Guide for 2022

Flat Roof Ventilation (Blog Cover)

Flat Roof Ventilation

Flat roof ventilation is essential because it helps maintain the health of your building, removes moisture and unsettling heat, and extends the roof’s lifespan. In addition, ventilation also increases HVAC unit efficiency and functionality.

Vents are readily discussed for residential roofs, but commercial flat roof ventilation information is more scarce. TPO and EPDM roofs can be hot or cold depending on where the insulation is installed

Hot roofs have insulation beneath the roof deck and over the material. In contrast, cold roofs have insulation beneath the roof deck and the roofing material.

Flat Roof Ventilation Benefits

We’ve noted some ways that ventilation helps maintain a high-performance flat roof for commercial building owners. Below, Roofer’s Guild outlines specific ways that ventilation benefits flat roofs in 2022.


Ventilation increases your flat roof’s lifespan and longevity by preventing condensation. Without ventilation, condensation can cause severe moisture damage and degrade the roofing material. As a result, proper ventilation reduces repair frequency and increases lifespan.

Energy Efficiency

Adequately ventilated flat roofs reduce heating and cooling costs for your commercial building. Summer can be incredibly stressful on energy costs, and a lack of proper ventilation will skyrocket your energy use. Additionally, keeping your building’s interior cooler puts less stress on your HVAC units while maintaining a comfortable temperature.

Interior Temperature Regulation

Your building’s interior temperature can impact the health and well-being of its occupants, along with goods or equipment stored inside. In addition, hot climates are prone to excessive heat that can degrade air quality. 

With flat roof ventilation, you can reduce temperature extremes inside your building and ensure a healthy temperature level regardless of outdoor fluctuations.

Cold Flat Roof Ventilation

Most cold roofs already have ventilation, allowing heat to escape underneath the shingles. As a result, the rest of the roof remains the same temperature as outside while the building stays protected. 

Since cold roofs are colder than your building’s interior during winter, condensation is less likely to form. 

Commercial Flat Roof Ventilation Tips

Commercial flat roofs need ventilation to prevent condensation. Even a thin layer of condensation can create significant problems for your building. It may rot your decking and materials and drip down to lower levels. Proper vent installation ensures roofs remain at the same temperature as the outside air.

Below are some FAQs regarding commercial flat roof ventilation:

How To Add Ventilation to a Flat Roof?

You need to circulate air in either the attic or the plenum to reach equal amounts of air exhaust and air intake. This enables the cavity to breathe, reducing problematic moisture and enhancing all aspects of the roof’s performance. For a visual example, see below:

How Much Ventilation Does a Flat Roof Need?

The absolute minimum required ventilation for a flat roof is 1 sqft per every 150 sqft of surface area. So, for example, a 200 sqft flat roof needs a minimum of 20 sqft of ventilation. But, of course, this is the bare minimum, and inverted gable fans are often a superior option.

A flat roof needs ventilation of a 25mm continuous gap running the entire length of both opposing eaves. Avoid cold bridging by extending the external walls to the insulation’s underside.

What is a Flat Roof Ventilation Strip?

A ventilation strip is installed into the soffit directly behind the gutter, allowing air to flow easily through the roof cavity and eliminate condensation and hot air.

What Type of Roof Ventilation Does a Flat Roof Have?

A flat roof can have the following types of roof vents:

  • Aura Vent: A long-lasting natural vent with zero moving parts is known for dynamically removing heat and moisture.
  • Boot Vent: A primary vent consisting of piping throughout the roof and quite popular because of its simplicity.
  • Box Vent: The aptly named box vent resembles its namesake and fits well with flat roofs because of the lack of pitch.
  • Pop Vent: A mechanical vent using an electric fan produces airflow with fresh external air.

Other kinds of vents used on flat roofs include breather vents, mushroom vents, and soffit vents.

Final Thoughts

A ventilated flat roof allows hot air to escape through the ridge and soffit vents. Hot air is trapped beneath the shingles and bleeds through the building’s interior without adequate ventilation. Entirely neglecting ventilation may cause melted rubber seals, severely damaging the roof.

Every commercial building owner should ventilate their flat roof to maintain indoor air quality, extend the roof’s lifespan, and avoid costly repairs. In addition, ventilation helps the roof maintain peak performance throughout its lifespan while reducing stress on your AC unit.